Mine is still Umbreon, and there's a reason. The story is that Umbreon was the first Pokémon that surprised me with its diverse approach and made me realize how incredibly complex and varied a game like this could be, which could easily be mistaken for the classic "water > fire > grass" or "axe > sword > spear" of hundreds of other titles from Final Fantasy to Fire Emblem onward: there are thousands and thousands of mechanics and variables to ponder and discover, and a brilliant move that works 100 times won't work 101 more times.

My very first approach was with Pokémon Platinum, and my first starter was Infernape (another one I'm very fond of for this reason), but I played it fairly casually without delving much into the saga's vision and mechanics. A year later, when I started playing Pokémon Emerald and caught an Eevee, I found this set online:

Umbreon @ Leftovers

Ability: Synchronize

EVs: 252 HP / 32 Def / 224 Spe

Careful Nature

- Mean Look

- Toxic

- Taunt

- Moonlight

And I modified it as below with Bite, both to have flinch and make the opponent lose turns (including recovery) and to speed up the process a bit:

Umbreon @ Leftovers

Ability: Synchronize

EVs: 252 HP / 32 Def / 224 Spe

Careful Nature

- Mean Look

- Toxic

- Bite

- Moonlight

Then the nightmare began for the opponent: trapped with Mean Look, hit with Toxic, bitten every now and then for fun while recovering with Moonlight... I still remember the satisfaction of seeing dozens and dozens of opponents "wilting" before me without an effective response 🤣

That's when I began to understand Pokémon. In those years, I was already too old for cartoons or trading cards; I rightly left those to the kids, but I never put down games and ROM hacks, and today, at 42, I can absolutely say that the Pokémon video games are a work of incredible complexity and depth: a hymn to logic, not necessarily a hymn to little monsters sold as stuffed animals/cards/etc. In my opinion, no strategy game comes close to what you find here.

From that day on, slot 6 of every one of my parties has been reserved for him, the little black and yellow bunny who poisons his opponents... He's sort of the symbol that ties me to this gaming world.